From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f46.google.com (mail-wg0-f46.google.com [74.125.82.46]) by kanga.kvack.org (Postfix) with ESMTP id 4FC2D6B006E for ; Tue, 9 Dec 2014 04:14:48 -0500 (EST) Received: by mail-wg0-f46.google.com with SMTP id x13so232353wgg.19 for ; Tue, 09 Dec 2014 01:14:47 -0800 (PST) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id lq1si1098572wjb.25.2014.12.09.01.14.47 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 09 Dec 2014 01:14:47 -0800 (PST) Message-ID: <5486BD85.1010903@suse.cz> Date: Tue, 09 Dec 2014 10:14:45 +0100 From: Vlastimil Babka MIME-Version: 1.0 Subject: Re: [PATCH 1/3] mm: page_isolation: remove redundant moving for isolated buddy pages References: <000101d01384$fac61240$f05236c0$%yang@samsung.com> In-Reply-To: <000101d01384$fac61240$f05236c0$%yang@samsung.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Weijie Yang , iamjoonsoo.kim@lge.com Cc: 'Andrew Morton' , mgorman@suse.de, 'Rik van Riel' , 'Johannes Weiner' , 'Minchan Kim' , 'Weijie Yang' , linux-kernel@vger.kernel.org, linux-mm@kvack.org On 12/09/2014 08:50 AM, Weijie Yang wrote: > The commit ad53f92e(fix incorrect isolation behavior by rechecking migratetype) > patch series describe the race between page isolation and alloc/free path, and > fix the race. > > Now, after the pageblock has been isolated, free buddy pages are already in > the free_list[MIGRATE_ISOLATE] and will not be allocated for usage. So the > current freepage_migratetype check is unnecessary and it will cause redundant > page move. That is to say, even if the buddy page's migratetype is not > MIGRATE_ISOLATE, the page is in free_list[MIGRATE_ISOLATE], we just move it > from free_list[MIGRATE_ISOLATE] to free_list[MIGRATE_ISOLATE]. > > This patch removes the unnecessary freepage_migratetype check and the > redundant page moving. > > Signed-off-by: Weijie Yang With great hope that Joonsoo won't find another corner case J Acked-by: Vlastimil Babka > --- > mm/page_isolation.c | 17 +---------------- > 1 file changed, 1 insertion(+), 16 deletions(-) > > diff --git a/mm/page_isolation.c b/mm/page_isolation.c > index c8778f7..6e5174d 100644 > --- a/mm/page_isolation.c > +++ b/mm/page_isolation.c > @@ -221,23 +221,8 @@ __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn, > continue; > } > page = pfn_to_page(pfn); > - if (PageBuddy(page)) { > - /* > - * If race between isolatation and allocation happens, > - * some free pages could be in MIGRATE_MOVABLE list > - * although pageblock's migratation type of the page > - * is MIGRATE_ISOLATE. Catch it and move the page into > - * MIGRATE_ISOLATE list. > - */ > - if (get_freepage_migratetype(page) != MIGRATE_ISOLATE) { > - struct page *end_page; > - > - end_page = page + (1 << page_order(page)) - 1; > - move_freepages(page_zone(page), page, end_page, > - MIGRATE_ISOLATE); > - } > + if (PageBuddy(page)) > pfn += 1 << page_order(page); > - } > else if (page_count(page) == 0 && > get_freepage_migratetype(page) == MIGRATE_ISOLATE) > pfn += 1; > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org